Machines and methods for labeling plastic containers by placing a label into a blow mold and then blow-forming the container are known. For example, U S. Pat. Nos. 4,355,967, 4,359,314 and 4,479,644 show machines which insert labels between open halves of blow molds which are mounted on the periphery of a wheel. After the labels have been inserted, preforms (i.e. tubes of hot extruded plastic) are introduced into the cavity. The molds are then closed and the container blown. The labels are bonded to the container, typically by means of a heat-activated adhesive on the back of the label.
U.S. Pat. No. 4,479,771 shows a machine whose blow molds are stationary, but which works in much the same way.
A machine similar to that shown in U.S. Pat. No. 4,479,771 is described in U.S. Pat. No. 3,292,209. The preforms in the '209 patent are said to be injection molded, however.
One known type of injection blow molding machine is that in which split parison and blow molds open along a common parting plane. Work pieces are first injection molded, then blown and removed at successive work stations. Transfer between work stations is accomplished by a turret, which moves in concert with the movable mold halves and rotates about an axis, about which the work stations are radially disposed. The turret has a number of sides (normally three or four) which corresponds to the number of work stations. Core rods or mandrels radially project from each of the turret sides toward the respectively facing work stations.
Such machines are widely used because of their efficiency and dependability, but heretofore have not been thought suitable for in-mold labeling because in all known machines of this type, the parison molds and blow molds open simultaneously just before the transfer stage. Thus the machine's cycle would have to be interrupted briefly while the label is inserted into the blow mold cavity. This is undesirable because it would slow production and because a parison normally should be blown as soon after its transfer as possible for consistent container quality.